Frame-type sprinklers are often installed extending downwardly through a ceiling from piping running above the ceiling. The piping supplies water or other fire-retarding fluid to the sprinkler.
Generally speaking, frame-type sprinklers include a frame having a pair of arms which are fixedly coupled with and extend away from a body of the sprinkler on either side of an outlet on the body. Ends of the arms remote from the sprinkler body are brought together at a joint or connect with a common cross member. The frame extends completely around the sprinkler outlet. Typically a temperature-sensitive element is biased against a plug positioned within the outlet by an adjustment screw extending through the joint or cross member. The joint or cross member further fixedly supports a water deflector spaced from the sprinkler outlet and typically protruding below the lower surface of the ceiling through which the sprinkler is installed to deflect water outwardly from the sprinkler at a level beneath the ceiling when the sprinkler activates.
Drop-type sprinklers are also installed through ceilings. In drop-type sprinklers, the fluid deflector plate is initially supported close to the sprinkler body at or above the ceiling line before the sprinkler is activated. The deflector drops from that position to a position below the ceiling line just before or at the same time as the activation of the sprinkler. The deflector is typically supported at the ends of guide pins or the like slidingly coupled with a flange portion of the sprinkler body or some other supporting structure also supported by the sprinkler body. The guide pins function like the fixed arms of the aforesaid frames in that they support the deflector in alignment with and spaced from the outlet.
Sprinklers are often installed in locations where aesthetics are a consideration, such as office buildings, schools, etc. To improve the appearance of such sprinklers, covers are preferred which hide the sprinkler and the ceiling opening while the sprinkler is not operating. During a fire, the cover must drop away from the sprinkler, at least by the time the sprinkler activates, so as not to interfere with the delivery of water or other fire-retarding fluid from the sprinkler body over the deflector.
One approach which has been widely used for securing a cover to a sprinkler so that the cover will disconnect from the sprinkler during the fire, has been to use temperature-sensitive seal means between a ceiling plate portion of the cover and a support or bracket member. This approach is shown, for example, in U.S. Pat. No(s). 3,393,746, 3,727,695, 3,998,273, and 4,215,751 disclosing frame-type sprinklers. It is also shown, for example, in U.S. Pat. No. 4,066,129 showing a drop-type sprinkler. In each instance, some ancillary structure, such as a housing, yoke, etc. formed on or coupled with the sprinkler body has been provided specifically to receive the ceiling cover. Two of the U.S. Pat. No(s). 3,393,746 and 4,215,751, disclose covers which are adapted to be adjustably positioned with respect to the sprinkler body and the deflector to compensate for the variations between the height of the sprinkler and the ceiling. Such variations typically arise during the installation of such sprinklers.
U.S. Pat. No. 4,926,946 discloses a drop-type ceiling sprinkler with cover in which one or more spring clips are wedged between the sprinkler body and the deflector. The clips engage and support a cover. When the sprinkler is activated, a plug valve assembly carrying the deflector drops from the sprinkler body, releasing the spring clips and dropping the cover.
Recently, a cover for frame-type sprinklers has been introduced which includes a generally circular ceiling plate having a pair of centrally located, opposing bracket members. Each bracket member is made from a metal alloy with heat-activated "memory". Each of the bracket members has a pair of spaced, upstanding, resilient arms, each arm has an upper edge turned inwardly towards the center of the cover. The inwardly turned edges can be snapped over a circular deflector supported on a frame-type sprinkler to support the cover directly from the deflector. When the cover is heated to a sufficiently high temperature, the memory of the alloy of the bracket members causes the bracket member arms to deflect radially outwardly, releasing the arms and cover from the deflector. The temperature-sensitive element used to trigger the activation of the sprinkler is then exposed to heat to which the cover was previously exposed.
A major advantage provided by the clip-retained cover of U.S. Pat. No. 4,926,946 and of this last-mentioned cover using "memory" alloy brackets is that, strictly speaking, neither requires any ancillary structure on the sprinkler, apart from the sprinkler body and the deflector, which are ordinarily provided. Each type of cover can be retroactively mounted to such sprinklers.
However, unlike the cover disclosed in U.S. Pat. No. 4,926,946, the memory alloy cover is not adjustable in height with respect to the sprinkler. The lack of an adjustment feature on the memory alloy cover places that cover at a distinct commercial disadvantage. Purchasers and potential purchasers are primarily interested in the provision of such covers for aesthetic reasons. Because it is impossible, or nearly impossible, to exactly position sprinklers with respect to the ceiling through which they extend, the memory alloy clip cover is likely to be noticeably spaced from the ceiling for a sprinkler installed lower than the maximum permitted height of the sprinkler.